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A couple of questions

  1. Jan 15, 2004 #1
    1. Is every quantity that has three components in three dimensions a vector? From the definition of a vector I think it is. If it isn't, can you give me an example?

    2. How can you tell if the projection of a force vector F along the velocity vector v of a particle is a scalar?
  2. jcsd
  3. Jan 15, 2004 #2
    It would be possible if it obeys vector law of addition
    Consider a current flowing through junction which is attached to three dimension network, it will have magnitude in 3 direction.
    But definitely current is a scalar quantity

    Projection along v will be fcos(theta)

    Now F.v=Fcos(theta)*v Therefore

    Fcos(theta)= (F.v)/v which is clearly scalar
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